1. Field of the Invention
This application relates to drives for reciprocating equipment along a work path and more particularly to a reel system for winding up and paying out two self-expanding coiled tapes to reciprocate equipment along a track for use in clarifier basins.
2. Discussion of Prior Art
In the past, clarifier basins have been provided with sediment collecting devices that move on a track fixed to the floor of the basin. In one such device, patented by applicant in U.S. Pat. No. 4,401,576, a carriage is provided for movement along the track. The carriage is moved by a stepping mechanism that grips the track and moves the carriage relative to the track. Although such stepping mechanism has been commercially successful, mechanisms that are located under water are inherently difficult to maintain because the track is located under water where the sediment or sludge collects on the floor of the clarifier basin.
In other devices for removing sludge from the floor of clarifier basins, floats are pulled alternately in opposite directions across the surface of the clarifier basin. Pipes extend from the float to the floor for sludge collection. The floats are pulled by a cable that has first and second ends. The first end is wound in one direction on a winch and the second end of the cable is wound in the opposite direction on the winch, such that rotation of the winch in one direction unwinds the first end of the cable and winds up the second end of the cable to pull the float in one direction across the basin. Reversing the direction of rotation of the winch reverses the direction in which the float is pulled across the basin. In the device of this type disclosed in U.S. Pat. No. 3,416,176 issued in 1968, the winch has a fixed diameter drum. Both the first and second ends of the cable are tightly wound on the drum of the winch. In this device, if the travel of the float is long enough to require the cables to wind on themselves and form more than one layer on the drum, the length of cable unwound from the now larger diameter on the drum will exceed that wound on the drum, which requires use of spring-biased pulleys, for example, to compensate for the unequal lengths.
In other clarifier basins that are provided with apparatus for removing sludge, the direction of movement of a bridge across the clarifier basin is reversed by reversing the direction of a drive motor. This occurs by tripping switches when the bridge reaches the end of its motion in a particular direction. In other devices for removing sludge from clarifier basins, an elongated power screw is mounted across the top of the clarifier basin. This screw is rotated by a motor. A ball nut actuator is threaded onto the power screw and is mounted on a carriage against rotation. When the motor rotates the power screw, the carriage is reciprocated over the top of the clarifier basin.
In other drives for reciprocating devices along a path, one end of a cable is wound in one direction on a drum and the other end of the cable is wound in the other direction on the drum. In one such unit disclosed in U.S. Pat. No. 630,962 issued in 1899, the drum is provided with three surfaces, the outer two of which surfaces are conical in shape for receiving a pair of cables that are wound in a first direction. The other surface, a central cylindrical drum, receives a sounding line that is wound in a direction opposite to that of the cables. This unit requires the use of cable guides that are provided on a lead screw for guiding the cables onto selected and controlled portions of the conical surfaces.
In the art of moving or lifting objects, the single drum of an ordinary hoist has been provided with a ring that divides the single drum into two sections. In one such apparatus disclosed in U.S. Pat. No. 747,113 issued in 1903, a button has been provided on such ring and is used for engaging a rope so that as both sections of the drum are rotated in the same direction, one section of the drum winds up one length of rope while the other section of the drum unwinds another length of rope.
In other drives for positioning transducers along a longitudinal path, such as disclosed in U.S. Pat. No. 4,198,871 issued in 1980, a capstan is provided with a cylindrical surface to which opposite ends of a flexible, steel belt are secured. Those ends of the belt are wrapped in opposite directions on the capstan so that rotation of the capstan in a given direction unwinds one end and winds up the other end. In this device, those ends are wound tightly on the capstan such that the belt does not become uncoiled when the direction of rotation of the capstan is changed.
In a swimming pool cleaning device disclosed in U.S. Pat. No. 2,646,889 issued in 1953, a vertically extending guide rod is used to support a cleaning head that is moved up and down within the swimming pool under the action of a manually operated winch. Cables are wound in the same direction on the winch such that rotation of the winch in a given direction winds in both of the cables to lift the cleaning head.
In a high speed printer disclosed in U.S. Pat. No. 3,872,960 issued in 1975, a motor drives a helically grooved pulley which has attached to it left and right cable segments of equal length. The other ends of the cable segments are attached to a movable careiage. One pulley of this system is spring biased to remove any slack from either of the cables which might occur due to long term temperature drift. Thus, both cable segments are held tight against the grooved pulley.